This invention relates to a deceleration control system suitable for use in automobiles provided with a continuously variable transmission commonly referred to as a CVT.
With the recent marked development of hydraulic pump/motors having high efficiency, it has become possible to greatly improve the performance of a hydrostatic transmission commonly referred to as an HST or a hydromechanical transmission commonly referred to as an HMT, which both comprise a combination of hydraulic pump/motors. Now the time is becoming ripe for application of these continuously variable transmissions to automobiles which require a transmission having a high performance characteristic.
In an automobile which employs such a continuously variable transmission, in principle the clutch should not be kept off while the automobile is running, and the transmission must have such a characteristic that when the accelerator pedal is released, the automobile is allowed to run by inertia as smoothly as if the clutch was off. When the brake pedal is operated, however, smooth and rapid deceleration should advantageously be effected. Since frequent use of the wheel brake is likely to cause the brake shoe to be heated and/or worn, it is advisable to make effective use of engine brake for deceleration.
Conventional automobiles employing a continuously variable transmission such as mentioned above are provided with a wheel braking system including a brake pedal which is operated independently of the operation of the system for controlling the reduction ratio of the transmission. This makes it impossible to control engine brake by the operation of stepping on the brake pedal and consequently to obtain the previously mentioned driving characteristics.
Accordingly, the primary object of the invention is to solve without fail and with a comparatively simple system the above mentioned problem that it is difficult to effect deceleration by making effective use of not only the wheel brakes but also engine brake.
The invention will be described with reference to the accompanying drawings .